Syringe-in-syringe hollow inner barrel/plunger with integral seal and rupturable membrane and related kits, systems, and methods

ABSTRACT

A plunger-barrel apparatus is adapted for use within a syringe-in-syringe mixing system for mixing a two-part composition (e.g., a dental composition). A hollow plunger-barrel body has a continuous cylindrical wall defining an internal chamber for containing a first component. The body includes a plunger receiving end and a dispensing end. An integral sealing plug and rupturable membrane is disposed at the dispensing end of the body and include a sealing plug portion and a rupturable membrane portion that are integrally formed together as a single piece (e.g., formed of a single piece of elastomeric material). An associated syringe-in-syringe mixing system includes a first plunger, the hollow plunger-barrel body as described above adapted to contain a first component, and a syringe barrel configured to contain a second component. When assembled, the first plunger is slidably disposed within the hollow plunger-barrel body, and the plunger-barrel body is slidably disposed within the syringe barrel. The two components are initially separated by the rupturable membrane.

RELATED APPLICATIONS

The present application is a continuation of copending U.S. patentapplication Ser. No. 11/673,334, filed Feb. 9, 2007, which is acontinuation-in-part of copending U.S. patent application Ser. No.11/414,964, filed May 1, 2006 and entitled “TIME-INDICATINGSYRINGE-IN-SYRINGE MIXING DEVICES AND RELATED METHODS FOR STORING ANDDISPENSING TWO-PART DENTAL COMPOSITIONS. The disclosures of theforegoing applications are incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

1. The Field of the Invention

The present application is directed to devices and methods for mixing,storing and dispensing two-part dental compositions.

2. The Relevant Technology

Many chemical formulations are packaged in two initially separate parts,often known as A and B components. Separate storage of the A and Bcomponents is often necessary where the composition resulting frommixing is unstable over time. For example, a self-etching dental primercomposition may be provided in two initially separate parts to preventthe acid component from slowly destabilizing the polymerizable resincomponent by hydrolyzing off the functional group(s) to which thebackbone of the resin is chemically bonded. Although suchdestabilization may not occur immediately upon mixing, with many suchcompositions, it is often recommended that the composition be used up ordiscarded within a certain time period (e.g., 30, 60, or 90 days) afterinitial mixing.

Because such compositions are unstable once mixed, it is important toensure that the two parts remain separated prior to mixing, so as toprevent premature mixing and destabilization. In addition, it is awkwardand time consuming for the practitioner to have to measure eachcomponent from a larger container, and then mix them together prior tointroducing the mixed composition into a storage and/or dispensingdevice. In light of the above, it would be an advantage to provide asyringe-in-syringe all in one mixing and dispensing system for use witha two-part composition that would provide a practitioner withpre-measured amounts of each component ready for mixing, and that wouldprovide the user with an all in one device that could easily beactivated to effect mixing, while also being used to store and laterdispense the composition. It would be a further advantage if theall-in-one mixing and dispensing device reduced the possibility ofpremature mixing of the components, while also being inexpensive andeasy to mass manufacture so as to be disposable after a single use.

BRIEF SUMMARY OF THE PREFERRED EMBODIMENTS

The present invention is directed to a hollow inner plunger for usewithin a syringe-in-syringe mixing system for mixing a two-part dentalcomposition. The hollow inner plunger includes a body having acontinuous cylindrical wall defining an internal chamber for containinga first component. The body includes a proximal end and a distal end. Asealing plug and rupturable membrane are disposed at the distal end ofthe body, and the sealing plug and rupturable membrane are integrallyformed together as a single piece (e.g., formed of a single piece ofelastomeric material).

Providing a sealing plug and rupturable membrane that are integral so asto comprise a single piece of material greatly simplifies the massmanufacture of the hollow inner plunger and a syringe-in-syringe mixingsystem of which it forms a part. The integral sealing plug andrupturable membrane provide a simple, low-cost way to ensure initialseparation of the two-parts of a two-part dental composition within thesyringe-in-syringe mixing system, while also minimizing and/orpreventing contamination that may otherwise occur if the rupturablemembrane were to comprise a separate part bonded to the distal end ofthe hollow inner plunger.

For example, any bonding adhesive used to bond a membrane may becontaminated or chemically attacked by one or both of the componentsseparated by the rupturable membrane causing weakening or failure of thebond (e.g., during storage). Furthermore, where the composition isintroduced into the chamber prior to bonding of the rupturable membrane,the composition may contaminate the wall or other surface to which themembrane is to be bonded, which may inhibit formation of a strong bond.In addition, any bonding adhesive may likewise contaminate or chemicallyreact with one or both of the two components to be separated, which mayrender the mixed composition less effective or otherwise unsuitable foruse. Therefore, providing an integral sealing plug and rupturablemembrane not only reduces the number of parts and steps required inassembly, but also reduces the likelihood of contamination of thetwo-part composition or any bonding adhesive.

The hollow inner plunger may comprise part of an associatedsyringe-in-syringe mixing system for use in mixing and dispensing atwo-part dental composition. Such a system includes a first plunger, thehollow inner plunger as described above, and a syringe barrel configuredto contain a second component. When assembled, the first plunger isslidably disposed in sealing engagement within the hollow inner plunger,and the hollow inner plunger is slidably disposed in sealing engagementwithin the syringe barrel. The first component is initially storedwithin the chamber of the inner hollow plunger separate from the secondcomponent which is stored within the chamber of the syringe barrel. Thetwo chambers are initially separated by the rupturable membrane.

In one embodiment, the internal chamber of the hollow inner plunger hasa diameter at the distal end of the body that is less than a diameter ofthe chamber at the proximal end. Preferably, this narrowing of diameteroccurs near the distal end of the body (e.g., adjacent to or near aproximal end of the integral sealing plug/rupturable membrane).Narrowing the diameter of the chamber significantly increases thepressure exerted by the first component against the rupturable membrane,which has been found to greatly aid in causing rupture of the membranein such a way that results in jetting of the first component into thesecond component. The result of such jetting action is nearinstantaneous mixing of the two components, particularly for tworelatively low viscosity liquids. As such, the internal diameter at thedistal end is preferably not more than about 75% of the largest diameterof the chamber (e.g., the diameter at the proximal end), more preferablynot more than about 50% of the largest diameter of the chamber (e.g.,the diameter at the proximal end), and most preferably not more thanabout 35% of the largest diameter (e.g., the diameter at the proximalend). The inventors have found that a diameter at the distal end (i.e.,adjacent the rupturable membrane) measuring about one-third that of thelargest diameter of the chamber (e.g., the diameter from the proximalend to a location adjacent the sealing plug where the diameter isabruptly narrowed) results in catastrophic rupture of the membrane andjetting of substantially all of the first component through therupturable membrane and into the second component to effect homogeneousmixing.

The actual thickness of the rupturable membrane depends on the strengthand other physical properties of the selected material, along with theconfiguration of any reduction in diameter leading up to the proximalend of the body where the membrane is located. The rupturable membranepreferably has a thickness ranging from about 0.0005 inch to about 0.04inch, more preferably from about 0.002 inch to about 0.025 inch, andmost preferably from about 0.005 inch to about 0.015 inch. For example,it has been found that a thermoplastic elastomer material having athickness from about 0.005 inch to about 0.010 inch is particularlypreferred for the reasons described above when the diameter of theinternal chamber is reduced adjacent the distal end to about one-thirdof its value at the proximal end.

These and other advantages and features of the present invention willbecome more fully apparent from the following description and appendedclaims, or may be learned by the practice of the invention as set forthhereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the manner in which the above recited and other benefits,advantages and features of the invention are obtained, a more particulardescription of the invention briefly described above will be rendered byreference to specific embodiments thereof which are illustrated in theappended drawings. Understanding that these drawings depict only typicalembodiments of the invention and are not therefore to be consideredlimiting of its scope, the invention will be described and explainedwith additional specificity and detail through the use of theaccompanying drawings in which:

FIG. 1A is a perspective view of an exemplary hollow inner plungerincluding an integrally formed sealing plug and rupturable membrane;

FIG. 1B is a close up cross-sectional view of a distal end of the hollowinner plunger including the integral sealing plug and rupturablemembrane of FIG. 1A;

FIG. 1C is a close up cross-sectional view of an alternative hollowinner plunger including an internal chamber of substantially constantdiameter along its entire length;

FIG. 2 is a perspective view of an exemplary syringe-in-syringe mixingsystem incorporating a hollow inner plunger according to the presentinvention;

FIG. 3A is a perspective view of an exemplary first plunger for use in asyringe-in-syringe mixing system, the first plunger including anexemplary locking mechanism to prevent pull-out of the first plungeronce it has been fully inserted within the hollow inner plunger;

FIG. 3B is a perspective view of an alternative first plunger includingan alternative locking mechanism;

FIG. 4A illustrates the first plunger being pressed into the hollowinner plunger so as to cause the rupturable membrane at the distal endof the hollow inner plunger to break, resulting in jet mixing of thefirst component into the second component;

FIG. 4B illustrates the first plunger in a locked configuration relativeto the hollow inner plunger so as to prevent pull-out of the firstplunger from the hollow inner plunger; and

FIG. 4C illustrates dispensing of a portion of the mixed two-partcomposition onto a pad for subsequent application to a desired surface.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS I. Introduction

In one aspect, the present invention is directed to a hollow innerplunger for use within a syringe-in-syringe mixing system for mixing atwo-part dental composition. The hollow inner plunger includes a bodyhaving a continuous cylindrical wall defining an internal chamber forcontaining a first component. The body includes a proximal end and adistal end. A sealing plug and rupturable membrane are disposed at thedistal end of the body, and the sealing plug and rupturable membrane areintegrally formed together as a single piece (e.g., formed of a singlepiece of elastomeric material).

The hollow inner plunger may comprise part of an associatedsyringe-in-syringe mixing system for use in mixing and dispensing atwo-part dental composition. Such a system includes a first plunger, thehollow inner plunger as described above, and a syringe barrel configuredto contain a second component. When assembled, the first plunger isslidably disposed in sealing engagement within the hollow inner plunger,and the hollow inner plunger is slidably disposed in sealing engagementwithin the syringe barrel. The first component is initially storedwithin the chamber of the inner hollow plunger separate from the secondcomponent which is stored within the chamber of the syringe barrel. Thetwo chambers are initially separated by the rupturable membrane.

II. Exemplary Hollow Inner Plungers

FIG. 1A is a perspective view of hollow inner plunger 100 having a bodyincluding a continuous cylindrical wall 102. The body and wall 102include a proximal end 104 and an opposite distal end 106. The interiorof wall 102 defines an internal chamber 108 configured to contain afirst component 110 a. A flange 112 is disposed at proximal end 104,while an integrally formed sealing plug and rupturable membrane 116 isdisposed at distal end 106. Advantageously, and as shown in FIG. 1B,sealing plug 114 and membrane 116 are integrally formed as a singlepiece, for example, from an elastomeric material. Rupturable membraneportion 116 caps and seals off the opening of the distal end of hollowinner plunger 100 at the point where sealing plug 114 terminates at theopening, forming an uninterrupted surface across the entirety of thesealing plug portion and the membrane portion so as to contain firstcomponent 110 a within chamber 108, keeping it separate from a secondcomponent until the user desires to effect mixing. Sealing plug 114 isdisposed on the outside of body wall 102, extending laterally around thedispensing end of hollow inner plunger 100. Sealing plug 114 terminatesat the opening of the dispensing end of hollow inner plunger 100 and isconfigured to plug within a syringe barrel (see FIG. 2) so as to sealthe proximal end of the syringe barrel when the hollow inner plunger 100is assembled into a syringe-in-syringe mixing system.

The distal portion of the body of hollow inner plunger 100 over whichsealing plug 114 is fitted advantageously includes an outwardlyextending annular ridge 118 near the dispensing end that prevents plug114 from being separated from hollow inner plunger 100 during rupture ofrupturable membrane 116. Sealing plug 114 includes a correspondingannular groove 120 configured to matingly engage ridge 118 so as tosecurely attach sealing plug and rupturable membrane 116 to the body ofhollow inner plunger 100.

Sealing plug 114 and rupturable membrane 116 may advantageously beformed of an elastomeric material (e.g., a thermoset elastomer orthermoplastic elastomer), which advantageously provides an excellentseal against a syringe barrel while also providing a desired strength torupturable membrane 116. Rupturable membrane 116 extends over thedispensing end of the hollow inner plunger at the point where sealingplug 114 terminates at the opening of the dispensing end, forming aflat, uninterrupted surface across the entirety of the sealing plug 114and membrane 116 at which surface sealing plug 114 and membrane 116 bothterminate such that membrane 116 seals off the distal end of hollowinner plunger 100, separating first component 110 a from a secondcomponent 110 b contained within a syringe barrel 128 (see FIG. 2) untilthe user intentionally ruptures membrane 116, causing first component110 a to be forced into syringe barrel 128, where the two components aremixed together.

Providing a sealing plug 114 and rupturable membrane 116 that areintegral so as to comprise a single piece of material greatly simplifiesthe mass manufacture of the hollow inner plunger 100 and asyringe-in-syringe mixing system of which it forms a part. The integralsealing plug 114 and rupturable membrane 116 provide a simple, low-costway to ensure initial separation of the two-parts of a two-part dentalcomposition within a syringe-in-syringe mixing system, while alsominimizing and/or preventing contamination that may otherwise occur ifthe rupturable membrane 116 and sealing plug 114 were to comprise twoseparate parts requiring bonding of each to the body or wall 102.

For example, any bonding adhesive used to bond a rupturable membrane towall 102 (or any other structure) may be contaminated or chemicallyattacked by one or both of the components separated by the rupturablemembrane (e.g., during storage). Such contamination or chemical reactionwould likely lead to weakening and/or failure of the bond holding themembrane in place. Furthermore, where the composition is introduced intothe chamber prior to bonding of the rupturable membrane, the compositionmay contaminate the wall or other surface to which the membrane is to bebonded, which may inhibit formation of a good bond.

In addition, any bonding adhesive may likewise contaminate or chemicallyreact with one or both of the two components intended for separationwithin a syringe-in-syringe mixing system, which may render onecomponent, both components, or the mixed composition less effective orotherwise unsuitable for use. Therefore, providing an integral sealingplug and rupturable membrane not only reduces the number of parts andsteps required to assemble a hollow inner plunger and an associatedsyringe-in-syringe mixing system, but also reduces the likelihood ofcontamination of the two-part composition or any bonding adhesive,either of which could render the mixing system and/or compositionuseless.

FIGS. 1B and 1C illustrate cross-sectional views of alternativeembodiments. FIG. 1B illustrates an example in which the inside diameterof the chamber 108 of hollow inner plunger 100 is reduced at thedispensing end adjacent to rupturable membrane 116, while FIG. 1Cillustrates an alternative example in which the diameter D of thechamber 108′ is not reduced, but is substantially constant along thelength of the chamber 108′ so that the diameter D adjacent membrane 116′and plug 114′ is substantially the same as the diameter D elsewherealong chamber 108′.

FIG. 1B shows a preferred embodiment in which the internal chamber 108of hollow inner plunger 100 has a diameter D_(S) at distal end 106 ofthe body that is less than a diameter D_(L) of the chamber at proximalend 104. As illustrated, preferably this narrowing of diameter occursnear the distal end 106 of the body. For example, in the illustratedembodiment, the narrowing of the chamber diameter occurs adjacent ornear the proximal edge of the sealing plug 114. Reducing the outsidediameter of the body wall 102 along this distal portion also providesspace for the receipt of sealing plug 114 in a way that presents anoverall outside diameter of the plunger 100 that is substantiallyconstant along the entire length (i.e., between proximal end 104adjacent flange 112 and distal end 106), with the exception of primaryand secondary sealing surfaces 122 a and 122 b, respectively, which areconfigured to seal against the inside surface of a syringe barrel. Suchan arrangement provides a tight fit of the inner plunger 100 within asyringe barrel (e.g., see FIG. 2), reducing any tendency of the innerplunger to wobble within the syringe barrel, which tendency may becomeparticularly pronounced further away from the sealing surfaces 122 a and122 b (e.g., near proximal end 104). In one embodiment sealing plugportion 114 fits cylindrically around the diametrically reduced portionof the distal end of hollow inner plunger 100 so as to terminate at theopening of the diametrically reduced distal end portion. Sealing plug114 may have a diameter that is essentially the same as the diameter ofthe inner hollow plunger 100 leading up to the diametrically reducedportion. Sealing plug 114 may further include at least one sealingsurface (e.g., surfaces 122 a and 122 b) to create a seal with theinside surface of a syringe barrel to prevent leakage of the componentsfrom the syringe barrel.

In addition, narrowing the diameter of chamber 108 significantlyincreases the pressure exerted by first component 110 a againstrupturable membrane 116, when force is selectively applied by a user toa plunger inserted within proximal end 104. Narrowing of diameter hasbeen found to greatly aid in causing rupture of membrane 116 in such away that results in jetting of first component 110 a into secondcomponent 110 b. The result of such jetting action is near instantaneousmixing of the two components, particularly for two relatively lowviscosity liquids.

As such, the internal diameter D_(S) at the distal end 106 is preferablynot more than about 75% of the diameter D_(L) at proximal end 104 andalong the remainder of chamber 108, more preferably not more than about50% of the diameter D_(L), and most preferably not more than about 35%of the diameter D_(L). The inventors have found that a diameter at thedistal end (i.e., adjacent the rupturable membrane) measuring aboutone-third that of the largest diameter of the chamber (e.g., thediameter is substantially constant from the proximal end 104 to alocation adjacent the sealing plug 114 where the diameter is abruptlynarrowed) results in catastrophic rupture of the membrane and jetting ofsubstantially all of the first component 110 a through the rupturablemembrane 116 and into the second component to effect homogeneous mixing.

The actual thickness of rupturable membrane portion 116 depends on thestrength and other physical properties of the selected material, alongwith the configuration of any reduction in diameter leading up to theproximal end of the body where the membrane is located. The rupturablemembrane portion preferably has a thickness ranging from about 0.0005inch to about 0.04 inch, more preferably from about 0.002 inch to about0.025 inch, and most preferably from about 0.005 inch to about 0.015inch. For example, it has been found that a rupturable membrane formedof a thermoplastic elastomer material having a thickness from about0.005 inch to about 0.010 inch is particularly preferred for the reasonsdescribed above when the diameter D_(S) of the internal chamber 108 isreduced adjacent the distal end 106 to about one-third of its value atthe proximal end 104.

III. Exemplary Syringe-in-Syringe Mixing Systems

FIG. 2 illustrates an exemplary syringe-in-syringe mixing system 124.System 124 includes a first plunger 126, a hollow inner plunger 100, anda syringe barrel 128 with a cap 130 at a distal end of syringe barrel128 (a plug fitting inside the distal end of barrel 128 couldequivalently be used). First plunger 126 is slidably disposed withinhollow inner plunger 100, which is slidably disposed within syringebarrel 128. As illustrated, hollow inner plunger 100 contains a firstcomponent 110 a, and syringe barrel 128 contains a second component 110b. First plunger 126 includes an elongate stem 132 and an associatedsealing plug 134 at a distal end of stem 132.

As perhaps best seen in FIG. 3A, a locking mechanism 136 mayadvantageously be included near a proximal end of first plunger 126 toprevent withdrawal of first plunger 126 from inner plunger 100 onceinserted. Such a locking mechanism is helpful as once the membrane isruptured, the device cannot be reused for mixing two components,although it can be used to dispense the mixed composition until all hasbeen dispensed. Locking first plunger within inner plunger 100 allowsthe dispensing device to operate as a syringe comprising a barrel andplunger, which simplifies dispensing by the user while also preventingslideout of the first plunger, which could result in loss, contaminationor waste of the mixed composition. Illustrated locking mechanism 136comprises a circumferentially extending portion of enlarged diameter 138(relative to the remainder of stem 132), with a plurality oflongitudinally extending interlock ribs 140. In use, interlock ribs 140are inserted into hollow inner plunger 100, where the ribs 140 biasagainst the inside wall 102 of hollow inner plunger 100. The system isconfigured such that when first plunger 126 is fully inserted intohollow inner plunger 100, circumferentially extending portion 138 restswithin flange 112 of hollow inner plunger 100, while interlock ribs 140extend distally into hollow inner plunger 100, past flange 112. Becauseflange 112 provides increased barrel strength relative to the remainderof hollow inner plunger 100, little or no deformation occurs to theinside wall of hollow inner plunger 100 on account of portion 138, butdeformation is caused by ribs 140, resulting in associated indentationsbeing formed into the inside wall 102 of hollow plunger 100 distal toflange 112, preventing, or at least inhibiting, later removal of firstplunger 126 from hollow inner plunger 100 (e.g., see FIG. 4B).

FIG. 3B illustrates an alternative first plunger 126′ including acylindrical elongate stem 132, and a sealing plug 134. The principledifference between the first plunger 126′ and first plunger 126 of FIG.3A and FIG. 2 is that first plunger 126′ includes an alternative lockingmechanism 136′ comprising an annular interlock ring 140′ rather than theenlarged diameter portion 138 and plurality of interlock ribs 140 of theembodiment of FIG. 3A. Similar to interlock ribs 140, annular interlockring 140′ causes the formation of an indentation or groove within theinside wall 102 of hollow inner plunger 100. Annular interlock ring 140′resides in the formed groove, preventing, or at least inhibiting, pullout of first plunger 126 once fully inserted into hollow inner plunger100. Other locking mechanisms (e.g., an interference fit of the firstplunger into the hollow inner plunger) may alternatively be used.

According to one method, a pre-measured, pre-filled syringe-in-syringemixing system (as shown in FIG. 2) may be manufactured by firstinserting first plunger 126 into hollow inner plunger 100 so that firstplunger 126 is slidably received within hollow inner plunger 100.Sealing plug 134 of first plunger 126 seals the proximal end of hollowinner plunger. First component 110 a may then be introduced intointernal chamber 108 of hollow inner plunger 100. Integrally formedrupturable membrane 116 and sealing plug 114 may then be placed overdistal end 106 of hollow inner plunger 100, effectively sealing firstcomponent 110 a within chamber 108. Next, hollow inner plunger 100 maybe inserted into syringe barrel 128 so that hollow inner plunger 100 isslidably received therein. Primary and secondary sealing surfaces 122 aand 122 b, respectively, form a seal to prevent passage of any fluidaround seal 114, while membrane 116 forms a seal to prevent passage ofany fluid through seal 114 until the membrane is intentionally rupturedby the user. Second component 110 b may then be introduced into syringebarrel 128 through the distal end of the barrel. Cap 130 may finally beplaced over the distal end of barrel 128 so seal the distal end.Assembly in such a manner prevents or at least minimizes the formationand entrapment of air bubbles within the chamber of the inner plunger100 and/or the syringe barrel 128, and is thus currently preferred.

IV. Exemplary Method of Use

FIG. 4A illustrates an exemplary syringe-in-syringe mixing system 124.When it is desired to effect mixing of the two-part composition, theuser may press first plunger 126 to cause plunger 126 to slide intohollow inner plunger 100 so as to compress first component 110 a. Once asufficient force is applied, pressure against the rupturable membraneportion causes rupture of membrane 116. Rupturable membrane 116 breakscausing first component 110 a to be expressed under pressure from hollowinner plunger 100, introducing first component 110 a into syringe barrel128 where it contacts and/or mixes with second component 110 b.

The force of such rupture and jetting of the first component 110 a intothe second component 110 b is sufficient to effect homogeneous mixing,such that no additional mixing (e.g., by shaking) is required,particularly where both components are low viscosity liquids. Althoughpreferred for use with liquid-liquid systems, first and secondcomponents 110 a and 110 b may each be a liquid, or one may be a solidpowder, as dictated by the characteristics of the two-part compositionto be mixed. The syringe-in-syringe mixer is particularly well suitedfor mixing together two relatively low viscosity liquids (e.g., lessthan about 100 centipoise, more preferably less than about 10centipoise, and most preferably less than about 3 centipoise), becauseof the ability of the system to cause one component to be forcefullyejected into the other component so as to effect mixing without anyadditional effort (e.g., shaking is not necessary). One contemplatedrelatively low viscosity liquid-liquid two-part composition is atwo-part self etching dental primer composition described in U.S. patentapplication Ser. No. 11/261,171, filed Oct. 28, 2005, and entitledSELF-ETCHING DENTAL PRIMER COMPOSITIONS AND METHODS AND SYSTEMSUTILIZING SUCH COMPOSITIONS, herein incorporated by reference.

Although particularly well suited for use with lower viscosity liquids,the system may also be used with higher viscosity liquids (e.g., up toabout 1000 centipoise or even up to about 3500 centipoise) or aliquid-solid powder two-part composition, although when used for mixingsuch two-part compositions further mixing beyond that provided by therupture of the membrane and turbulent jetting of one component into theother may be necessary. For example, it may be helpful when mixing sucha composition to remove cap 130 and couple the system to another syringeso as to allow syringe-to-syringe mixing of the composition.

In other words, the rupturable membrane 116 is configured to only passfirst component 110 a for mixing with second component 110 b under apressure sufficiently high to cause jetting of the first component intothe second component (e.g., so as to create turbulence sufficient to mixthe two components together). Cap 130 may include a check-valve or othervent (not shown) that permits air or other gas within barrel 128 to beexpelled as first component 110 a is expressed into barrel 128. Anycheck-valve known in the art can be used or modified to attach to barrel128.

The system may advantageously be configured such that a force requiredto rupture membrane 116 is approximately equal to a force required toinsert and lock locking mechanism 136 (i.e., enlarged diameter portion138 and interlocking ribs 140) of the cylindrical elongate stem 132 intohollow inner plunger 100, although it is not required. Such aconfiguration provides a smooth and continuous movement and feel duringuse of the system as first plunger 126 is pressed into hollow innerplunger 100, rupturing membrane 116 and locking first plunger 126 intohollow inner plunger 100, all within a single movement. FIG. 4Billustrates the system once first plunger 126 has been fully insertedinto hollow inner plunger 100. In this configuration, first plunger 126is locked into hollow inner plunger 100.

In the locked configuration as shown, it is difficult, if notimpossible, to withdraw first plunger 126 from hollow inner plunger 100without destroying the system. Enlarged diameter portion 138 is disposedwithin the center of flange 112, while ribs 140 extend distally fromflange 112 further into hollow inner plunger 100. Because flange 112 hasincreased barrel strength relative to the area of hollow inner plunger100 immediately distal to flange 112, the inside wall surface 102 ofhollow inner plunger will be deformed by ribs 140 so as to form adepression into the portion of the contacted inside wall 102. At thesame time, the inside wall surface 102 of hollow inner plunger 100directly under flange 112 will be deformed only slightly if at allbecause of the increased barrel strength of the flange region 112compared to the region contacted by ribs 140. In other words, ribs 140create an interlock with the inside surface of hollow inner plunger 100,preventing, or at least inhibiting, subsequent withdrawal of firstplunger 126 from hollow inner plunger 100.

FIG. 4C illustrates the system 124 with a dispensing tip 142 coupled ata distal end of barrel 128 so as to allow the user to dispense the mixedtwo-part composition 110. As locked, hollow inner plunger 100 and firstplunger 126 may together be used to function as a second plunger forsyringe barrel 128. As illustrated, composition 110 may be dispensedonto a pad for subsequent application (e.g., with a brush tool).Alternatively composition 110 may be dispensed directly onto a tooth orother surface, depending on the preference of the user.

It will be appreciated that the present claimed invention may beembodied in other specific forms without departing from its spirit oressential characteristics. The described embodiments are to beconsidered in all respects only as illustrative, not restrictive. Thescope of the invention is, therefore, indicated by the appended claimsrather than by the foregoing description. All changes that come withinthe meaning and range of equivalency of the claims are to be embracedwithin their scope.

1. A plunger-barrel apparatus for use in a syringe-in-syringe mixing system adapted for mixing a two-part composition, the plunger-barrel apparatus comprising: a hollow plunger-barrel body sized and configured for insertion into a syringe barrel and having a continuous wall defining an internal chamber for containing a composition therein, the hollow plunger-barrel body having a plunger receiving end and a dispensing end, the plunger receiving end having an opening sized and configured for receiving therethrough a sealing plug of an auxiliary plunger; and an integrally formed sealing plug and rupturable membrane disposed over the dispensing end of the hollow plunger-barrel body, the integrally formed sealing plug and rupturable membrane including: a sealing plug portion laterally disposed around the dispensing end of the hollow plunger-barrel body and having a distal end that terminates at or near an opening through the dispensing end and an outer surface that is adapted to sealingly engage against an inner surface of a syringe barrel; and a rupturable membrane portion integrally joined with the sealing plug portion and forming an uninterrupted surface across the distal end of the sealing plug portion so as to seal the dispensing end of the hollow plunger-barrel body and prevent passage of a composition through the dispensing end in the absence of irreversibly rupturing the rupturable membrane portion through application of pressure to a composition contained within the internal chamber.
 2. A plunger-barrel apparatus as recited in claim 1, wherein the internal chamber has a diameter at the dispensing end of the hollow plunger-barrel body that is less than a diameter of the internal chamber at the plunger receiving end.
 3. A plunger-barrel apparatus as recited in claim 1, wherein the internal chamber has a diameter at the dispensing end of the hollow plunger-barrel body that is not more than about 75% of the diameter of the internal chamber at the plunger receiving end.
 4. A plunger-barrel apparatus as recited in claim 1, wherein the internal chamber has a diameter at the dispensing end of the hollow plunger-barrel body that is not more than about 50% of the diameter of the internal chamber at the plunger receiving end.
 5. A plunger-barrel apparatus as recited in claim 1, wherein the internal chamber has a diameter at the dispensing end of the hollow plunger-barrel body that is not more than about 35% of the diameter of the internal chamber at the plunger receiving end.
 6. A plunger-barrel apparatus as recited in claim 1, wherein the integrally formed sealing plug and rupturable membrane comprise an elastomeric material.
 7. A plunger-barrel apparatus as recited in claim 1, wherein the integrally formed sealing plug and rupturable membrane comprise a thermoplastic elastomer or a thermoset elastomer.
 8. A plunger-barrel apparatus as recited in claim 1, wherein the rupturable membrane portion has a thickness between about 0.0005 inch and about 0.04 inch.
 9. A plunger-barrel apparatus as recited in claim 1, wherein the rupturable membrane portion has a thickness between about 0.002 inch and about 0.025 inch
 10. A plunger-barrel apparatus as recited in claim 1, wherein the rupturable membrane portion has a thickness between about 0.005 inch and about 0.015 inch.
 11. A plunger-barrel apparatus as recited in claim 1, further comprising a finger-engaging flange disposed at the plunger receiving end of the hollow plunger-barrel body.
 12. A plunger-barrel apparatus as recited in claim 1, wherein the hollow plunger-barrel body further includes an outwardly extending annular ridge disposed at or near the dispensing end and the sealing plug portion further includes a corresponding annular groove configured to matingly engage the annular ridge so as to attach the integrally formed sealing plug and rupturable membrane over the dispending end of the hollow plunger-barrel body.
 13. A plunger-barrel apparatus as recited in claim 1, further comprising an auxiliary plunger that is receivable within the interior chamber and including a sealing plug that is adapted to sealingly engage against an inner surface of the continuous wall of the hollow plunger-barrel body.
 14. A plunger-barrel apparatus as recited in claim 13, further comprising a composition within the interior chamber and wherein the sealing plug of the auxiliary plunger is received within the interior chamber, wherein the integrally formed sealing plug and rupturable membrane prevents passage of the composition through the dispensing end of the hollow plunger-barrel body in the absence of irreversibly non-resealably rupturing the rupturable membrane member by applying pressure to the composition by the auxiliary plunger.
 15. A plunger-barrel apparatus as recited in claim 14, further comprising a syringe barrel containing a second composition, wherein the sealing plug member sealingly engages against in inner surface of the syringe barrel, the integrally formed sealing plug and rupturable membrane.
 16. A plunger-barrel apparatus for use in a syringe-in-syringe mixing system adapted for mixing a two-part composition, the plunger-barrel apparatus comprising: a first plunger having a plunger stem, a finger engaging flange at a proximal end of the stem, and a sealing plug at a distal end of the stem; a hollow plunger-barrel body sized and configured for insertion into a syringe barrel and having a continuous wall defining an internal chamber for containing a composition therein, the hollow plunger-barrel body having a plunger receiving end and a dispensing end, the plunger receiving end having an opening sized and configured for receiving therethrough the sealing plug of the first plunger, wherein the internal chamber has a diameter at the dispensing end of the hollow plunger-barrel body that is less than a diameter of the internal chamber at the plunger receiving end; and an integrally formed sealing plug and rupturable membrane disposed over the dispensing end of the hollow plunger-barrel body, the integrally formed sealing plug and rupturable membrane including: a sealing plug portion laterally disposed around the dispensing end of the hollow plunger-barrel body and having a distal end that terminates at or near an opening through the dispensing end and an outer surface that is adapted to sealingly engage against an inner surface of a syringe barrel; and a rupturable membrane portion integrally joined with the sealing plug portion and forming an uninterrupted surface across the distal end of the sealing plug portion so as to seal the dispensing end of the hollow plunger-barrel body and prevent passage of a composition through the dispensing end in the absence of irreversibly rupturing the rupturable membrane portion through application of pressure to a composition contained within the internal chamber.
 17. A plunger-barrel apparatus as recited in claim 16, wherein the internal chamber has a diameter at the dispensing end of the hollow plunger-barrel body that is not more than about 75% of the diameter of the internal chamber at the plunger receiving end.
 18. A plunger-barrel apparatus as recited in claim 16, further comprising a composition within the interior chamber and wherein the sealing plug of the first plunger is received within the interior chamber, wherein the integrally formed sealing plug and rupturable membrane prevents passage of the composition through the dispensing end of the hollow plunger-barrel body in the absence of irreversibly non-resealably rupturing the rupturable membrane member by applying pressure to the composition by the first plunger.
 19. A plunger-barrel apparatus as recited in claim 18, further comprising a syringe barrel containing a second composition, wherein the sealing plug member sealingly engages against in inner surface of the syringe barrel, the integrally formed sealing plug and rupturable membrane.
 20. A syringe-in-syringe mixing system for use in mixing a two-part composition comprising: a first plunger having a plunger stem and a sealing plug at a distal end; a hollow plunger-barrel body sized and configured for insertion into a syringe barrel and having a continuous wall defining an internal chamber for containing a first composition therein, the hollow plunger-barrel body having a plunger receiving end and a dispensing end, the plunger receiving end having an opening sized and configured for receiving therethrough the sealing plug of the first plunger; and an integrally formed sealing plug and rupturable membrane disposed over the dispensing end of the hollow plunger-barrel body, the integrally formed sealing plug and rupturable membrane including: a sealing plug portion laterally disposed around the dispensing end of the hollow plunger-barrel body and having a distal end that terminates at or near an opening through the dispensing end and an outer surface that is adapted to sealingly engage against an inner surface of a syringe barrel; and a rupturable membrane portion integrally joined with the sealing plug portion and forming an uninterrupted surface across the distal end of the sealing plug portion so as to seal the dispensing end of the hollow plunger-barrel body and prevent passage of a composition through the dispensing end in the absence of irreversibly rupturing the rupturable membrane portion through application of pressure to a composition contained within the internal chamber; and a syringe barrel configured to contain therein a second component, the syringe barrel being configured to slidably receive the hollow plunger-barrel body therein in sealing engagement and having a proximal opening configured to receive the integrally formed sealing plug and rupturable membrane therethrough.
 21. A syringe-in-syringe mixing system as recited in claim 20, further comprising a locking mechanism for preventing, or at least inhibiting, the first plunger from being withdrawn from the hollow plunger-barrel body once fully inserted therein.
 22. A syringe-in-syringe mixing system as recited in claim 21, wherein the locking mechanism comprises a plurality of interlock ribs formed near a proximal end of the first plunger, the plurality of interlock ribs being configured for insertion into the hollow plunger-barrel body so as to prevent or at least inhibit the first plunger from being withdrawn once the plurality of interlock ribs have been inserted into the hollow plunger-barrel body.
 23. A syringe-in-syringe mixing system as recited in claim 21, wherein the locking mechanism comprises an annular interlock ring formed near a proximal end of the first plunger, the annular interlock ring being configured for insertion into the hollow plunger-barrel body so as to prevent or at least inhibit the first plunger from being withdrawn once the annular interlock ring has been inserted into the hollow plunger-barrel body. 